Table 1.
Number of extracted teeth included in the study according to the tooth type and root morphology.
| Tooth type | Single-rooted | Double-rooted | Σ |
|---|---|---|---|
| Upper 1st/2nd premolar (N) | 8 | 20 | 28 |
| Lower 1st/2nd premolar (N) | 24 | 0 | 24 |
| Premolars (N) | 32 | 20 | 52 |
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